I've got a pair of Seas CA21RE 8" woofers and have been playing with Sonotubes...I have them mound push-pull in a 48"x10" tube running passive right now. If I mount them separately will I get enough SPL to keep them passive? Or should I keep this arrangement and get a plate amp? Right now they are sharing my NAD 3020 with Boston A60s.
thanks!
thanks!
If you are looking for more output I would try a push push configuration with the drivers facing out on each end of the sonotube. You could stand the sonotube up to reduce the amplitude of room modes.
Dan
Dan
Neato! How does that config boost output? I assume if they were wired in phase I would lose the push-pull harmonic cancellation?
owdi said:
..push-push in that configuration would be a dipole. It would reduce output (spl).
..push-pull in that configuration would increase output above the T-line's output and reduce output starting a bit below the T-line's output.
GhettoSQ said:
short answer:
mount each in their own tube with correct lengths for the driver's fs (..and dampen the tubes with fiber fill);
if stereo then connect each to their own plate amps, if mono connect the drivers in parallel to a single plate amp;
plate amps are cheap. In particular note this thread:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=76982
I'd be interested in the long answer too, since I always want to know why something is 🙂 I had seen a few project sites with push-pull setups they raved about, but Mr. Pass and our own GM recommended dual tubes.
The trick is, it will be a few months before even a $50 plate amp is in my Spouse Acceptance Factor parameters. So I was hoping the dual tubes might be a lot better passive than one push-pull...or at least wondering. I suppose the best approach is to wait, get an amp, and try different tube configs; sounds like it will be impossible to compare passive setups.
For the record, she calls it "El-poop-o." 😀
The trick is, it will be a few months before even a $50 plate amp is in my Spouse Acceptance Factor parameters. So I was hoping the dual tubes might be a lot better passive than one push-pull...or at least wondering. I suppose the best approach is to wait, get an amp, and try different tube configs; sounds like it will be impossible to compare passive setups.
For the record, she calls it "El-poop-o." 😀
GhettoSQ said:
Well for that then we would need to exactly how the drivers are utilized.
IF its like Pass's first "legend of el pipe-o" then the 2nd order distortion cancelation via push-pull operation is at best minimal. (..the reasons are complex - basically the pipe operates in a not to disimilar fashion to a a push-pull configuration, utilizing both methods at the same time substantially counteracts the effectiveness of the push-pull operation.)
Furthermore the pipe with 2 drivers will not exhibit as strong an spl in the pipe's range of operation when compared two pipes (which effectivly double spl, almost +3db, at these lower freq.s).
And sure, you can use two pipes with drivers connected together in parallel and hooked up to your current amp - essentially the same as you currently have. With this you should be able to increase the spl of lower freq. response by almost +3db as mentioned above. There are of course several reasons to buy a plate amp, but if you can't "swing" the purchase right now thats OK - it will still be worthwhile going the two pipe route.
ScottG said:
Wow, interesting. Seems like I saw a lot of tube projects with push-pull drivers, though? like this: http://www.teresaudio.com/haven/subs/subs.html
what do you mean by how they are utilized? right now they are mounted clamshell, out of phase, with the in-phase woofer downfiring. Sag is about 4.8%.
I thought the whole point was to guide the back wave, but Pass has his second version firing up. Sure would be easier for mounting since that way you don't need a box on the bottom. at the end he says:
"If you have an 8 foot ceiling, you can make two out of a 12 foot piece of 8 inch diameter, and find yourself decent 8 inch woofers resonant at about 40 Hz."
These drivers' relevant specs are:
Qts: .48
Vas: 81.3l or 2.871cu.ft.
Fs: 31Hz
Quarter-wavelength at Fs is 9 feet or so, I suppose I could fold an 8 inside a 10 (tubes). But it seems like with room gain a lot of folks prefer to tune for a bit above that. I estimate about 50-60Hz with a 48" tube stuffed...
GhettoSQ said:
"How they are utilized".. by that I mean do both drivers:
1. exit in-phase to the room?..and,
2. exit reverse-phase to the pipe?
Pass's second version is better with respect to distortion and T-line operation. (i.e. place the driver on the end like Pass has in the second version.) Note that you can further dampen the driver's resonance and its fs with a HIGHLY stuffed pipe. (i.e. less distortion and a more extended response.) The downside is that you will loose some efficiency and should utilize a slightly longer pipe. Furthermore the sub becomes less suitable for extended operation at higher freq.s.
Do NOT shorten the length of the pipe.. consider horizontal placement in-room instead (i.e. "running" along the bottom edge of the room). Conversly, consider a folded or spiral line.
ScottG said:
Not exactly sure. One is mounted in the pipe, down-firing, in phase with the mains. The other is mounted in front of it (under), reverse-phase.
It sounds like as long as I'm going to be passive for a bit it's worth a try. Should I do 2 8" tbes or 2 10" tubes?
I could buy a third tube of either size, cut it in half, attach the halves to the originals (good place for some kind of stuffing-stopper) and have 2 72" tubes. with 8" tubes this gives me a Vb of 2.094cu.ft, still a little under Vas.
GhettoSQ said:
Yeah.. I'm not sure what you have described either..
2 10 foot tubes if possible with LOTS of stuffing (compressed in the tube).. a driver on one end for each tube.
Note that IF you have 21 feet of room length for two 10 foot tubes near end to end then you can still get push-pull operation from the drivers..
i.e. Length of room 22 feet or more, width.. whatever.
Along one wall length (spanning near 22 feet positioned next to the wall and the floor):
1 tube with driver on one end.. T-Line end is about a foot away from the corner, driver end is about centered along the wall's length (minus 2 inches).
Next tube with driver on one end.. T-line end is about a foot away from the other corner on that wall, driver end is about 3-4 inches from the other tubes driver end.
The way I have it looks like the second el-pipe-o but the "in phase" driver is inside the tube, hidden above the bottom driver, firing down, back wave going up the line. No idea about the phasing relative to the room.
I don't have hardly that much room space
a 6' tube will give me an untuffed QW Fc of 47Hz - how far can stuffing really bring it down?
I'm still confused about the Vas/Vb relationship. Pass says get 2 6' 8" tubes, though when I switched from an 8" tube to 10" the bass definitely got deeper.
With 2 pipes space will become more of an issue. I can envision 2 8" pipes but 2 10s may be a tight fit. Ahh, city living. What will be the sonic (and mathematical) difference?
thx for the help BTW -- bear with me, I'm very n00bish.
I don't have hardly that much room space
a 6' tube will give me an untuffed QW Fc of 47Hz - how far can stuffing really bring it down?I'm still confused about the Vas/Vb relationship. Pass says get 2 6' 8" tubes, though when I switched from an 8" tube to 10" the bass definitely got deeper.
With 2 pipes space will become more of an issue. I can envision 2 8" pipes but 2 10s may be a tight fit. Ahh, city living. What will be the sonic (and mathematical) difference?
thx for the help BTW -- bear with me, I'm very n00bish.
GhettoSQ said:The way I have it looks like the second el-pipe-o but the "in phase" driver is inside the tube, hidden above the bottom driver, firing down, back wave going up the line. No idea about the phasing relative to the room.
I don't have hardly that much room space
I'm still confused about the Vas/Vb relationship. Pass says get 2 6' 8" tubes, though when I switched from an 8" tube to 10" the bass definitely got deeper.
With 2 pipes space will become more of an issue. I can envision 2 8" pipes but 2 10s may be a tight fit. Ahh, city living. What will be the sonic (and mathematical) difference?
thx for the help BTW -- bear with me, I'm very n00bish.
When in doubt measure - at least twice. (..i.e. what's the length of your listening room?)
It sounds like you either have a push-pull config or a push-push config.. either of which in that particular configuration is pointless in a T-Line. And yes, you will experince a gain in eff. over more than simply the T-Line's output with a 2 pipe setup over what you currently have.
In practice a T-line needs to be just about the a quarter of the wavelength (maybe +/- 5%) for reasonable extension provided by the pipe. So yes, it is important - perhaps not for modest extension at level to about the driver's fs, but definitly for increased extension below the driver's fs (..even if not at level). (..and here a large amount of stuffing helps considerably to extend the response.)
Try using Martin King's spreadheet if you want to sim it. (..I do NOT however recomend an "aligned" configuration that the sim can provide.) (..note I don't remember the last time I used it if it allows adjustment for the amount of fill - which is important.)
http://www.quarter-wave.com/
listening room is 12'x14', I believe. Even after reading MJK for Dummies I can't make heads or tails of the finer points :bang: I also don't have Excel.
But, I figured especially running passive, frequency overlap is my friend here. I was simply worried about losing the quality of the harmonic cancellation effect of my current setup (push pull). There are enough push-pull pipe projects out there that it seemed like a good idea, but what you say makes sense.
As for tuning frequency, John Risch suggested in his RoT that moderate-to-high-Qts drivers be tuned below Fs, but I've seen GM and others suggest sqrt2*fs, which is 43.5Hz for me. I'm stuck with a passive crossover at (I think) about 350Hz (ugh), but these drivers have good midbass behavior so maybe a higher tuning frequency is ok for now? I may be able to get the amp soon-ish, at which point perhaps I should do an eccentric folded line.
But, I figured especially running passive, frequency overlap is my friend here. I was simply worried about losing the quality of the harmonic cancellation effect of my current setup (push pull). There are enough push-pull pipe projects out there that it seemed like a good idea, but what you say makes sense.
As for tuning frequency, John Risch suggested in his RoT that moderate-to-high-Qts drivers be tuned below Fs, but I've seen GM and others suggest sqrt2*fs, which is 43.5Hz for me. I'm stuck with a passive crossover at (I think) about 350Hz (ugh), but these drivers have good midbass behavior so maybe a higher tuning frequency is ok for now? I may be able to get the amp soon-ish, at which point perhaps I should do an eccentric folded line.
GhettoSQ said:
350 Hz is a SERIOUS problem. ..and another reason to pony up the change for a plate amp (..even a cheap one). With that problem I'd point you in the direction of bandpass subwoofer - except that it would cost more in materials to make the bandpass box then it would to simply buy the cheap plate amp. (..additionally the sound quality would be inferior).
At this point I'm at a loss for further suggestions. 🙄
Note that MJK's spreadheet is for MathCad Explorer 8 (..which can be downloaded for free.)
Well, it doesn't sound like 350Hz, it sounds a lot lower when I put my ear to it. The midbas out of the mains is pretty good too. It's a 2-way/12db, 5mh coils and 110uf caps. I haven't been able to figure it out on the web, but it works well enough for now. This is all proof-of-concept at this point.
I agree about the bandpass box, no good. I will try the MJK stuff to get a better sense of things but will likely buy a few more tubes and try it stereo before buying an amp. Then I can do it all again!
So, can you give me a better idea of Vas vs. Vb, or why a 10" pipe will be better than an 8"?
Thanks again, this is all extremely helpful 🙂
I agree about the bandpass box, no good. I will try the MJK stuff to get a better sense of things but will likely buy a few more tubes and try it stereo before buying an amp. Then I can do it all again!
So, can you give me a better idea of Vas vs. Vb, or why a 10" pipe will be better than an 8"?
Thanks again, this is all extremely helpful 🙂
GhettoSQ said:
Your welcome!
To get a better idea of pipe length (and paramaters in general) use Martin's program. (..a little modeling is worth more than a thousand words.) I'd play with it some and see what you come up with, then factor in room gain and see what the net result is. Then I would contact Scottmoose on the fullrange forum here and ask him to model your best result to see what he comes up with and see if there is room for improvement (..he has acess to the newer version of Martin's program). Only then would I consider making purchasing decisions.
(note that my only reason for an increase in pipe length beyond 1/4 of the fs wavelength is because fiber tends to lower fs - therefor requireing an increase in pipe length for an optimal result.)
OK, that makes sense...is the free wrksheet available anywhere? his newer ones need a license. I was thinking I might play with Hornresp instead...
GhettoSQ said:
I looked all over - it doesn't appear that he is offering the free version anymore.. At this point I'd contact Scottmoose.
After poring over Martin's alignment tables, it seems as if the ideal design would be 2 6 foot tubes made out of (each) on 4' tube and half another 4' tube, with the driver in between for offset?
I understand about the harmonic cancellation of the tube now, but I remember that push-pull cancels even harmonics while it looks like the tube will cancel odds? 3/4 wave, 7/4 wave, etc. Or is it "een" like the 2nd harmonic (3/4 wave) thus rendering push-pull useless?
I understand about the harmonic cancellation of the tube now, but I remember that push-pull cancels even harmonics while it looks like the tube will cancel odds? 3/4 wave, 7/4 wave, etc. Or is it "een" like the 2nd harmonic (3/4 wave) thus rendering push-pull useless?
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